Apparatus for railway train communication system



Feb. 23, 1943. 2,312,051

APPARATUS FOR RAILWAY TRAIN COMMUNICATION SYSTEMS W. P. PLACE '2 Sheets-Sheet 1 Filed April 15 1942' We?! flaw. 0 1170211224 His Feb. 23, 1943.

w. P. PLAQlf- APBARATUS for: RAILWAY TRA'IN COMMUNICATION SYSTEMS '2 Sheets-Sheet 2 I 1 l I l I I I l I I l I Ill Filed April'l5, 1942 Patented Feb. 23, 1943 APPARATUS FOR RAILWAY TRAIN COMMUNICATION SYSTEMS Willard P. Place, Penn Township, Allegheny County, Pa., assignor to The Union Sw tch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application April 15, 1942, Serial N 0. 439,002

13 Claims.

My invention relates to apparatus for railway train communication systems, and more specifically to apparatus to facilitate the transmission of communication current of a railway train communication system.

There are railway train communication systems which utilize the track rails as part of a transmitting circuit, the receiving apparatus of a station located on a train being effectively energized due to such communication current flowing in the rails and the transmitting apparatus of such train carried station being effective to supply such current to the rails. The low ballast resistance and the relatively high rail impedance cause a high attenuation for such current, with the result that a relatively high energy level output of the transmitting apparatus and high amplification by the receiving apparatus are required if reliable communication is to be assured between stations separated a distance of the order of a few miles.

An object of my present invention is the provision of novel and improved means to facilitate the transmission of communication current along a railway.

Another object of my invention is the provision of novel repeater facilities wherewith transmission of communication current over relatively long distances along a railway can be accomplished.

' Another object of my invention is the provision of improved means for coupling a line wire with-the rails of one or more tracks of a railway to facilitate the transmission of communication current to and from trains moving on such tracks.

Other objects and advantages of my invention will be apparent as the specification progresses.

In practicing my invention I provide a line cir cuit which includes one or more line wires extending along a railway and repeater equipment at each of one or more preselected locations. Each repeater equipment is connected to the line wires to repeat in the line wires in amplified form the communication current supplied to the line wires at some point so far distant from the repeater station that the current has become attenuated to a relatively low value. I also provide circuit connections at various points preselected with respect to the locations of the repcater equipments and each of which circuit connections is interposed between the line Wires and the rails of each of the tracks of the rail way for transfer of such communication current between the line wires and the track rails so that eifective and reliable communication with trains can be accomplished due to the amplification of the current bythe repeater equipment.

I shall describe three forms of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. l is a diagraI-mnatic view showing one form of apparatus embodying my invention when used with a pair of line wires for transmission of communication current along a multiple track railway. Fig. 2; is a diagrammatic view showing another form of apparatus embodying my invention when used with a single line wire extending along a railway track. Fig. 3 is a diagrammatic view showing a third form of apparatus embodying my invention when used for transmission of communication current from an ofiice to any train of a division of an associated railway.

In each of the difierent views like reference characters are used to designate similar parts.

Referring to Fig. 1, the tracks I, 2, 3 and 4 represent. four tracks of a multiple track railway, tracks I and 2- being those normally used for'westbound traffic, and tracks 3 and 4 being those normally used for eastbound trafiic. The track rails of each of these tracks would preferably be bonded in the usual manner to improve their conductivity. Each track may be formed into track sections for signaling purposes, but such use of the track rails is independent of their use for transmission of communication current. Tracks l and 4 are shown as occupied bytrains VI and V2, respectively, and each of which trains is equipped with communication apparatus including transmitting apparatus TA and receiving apparatus RA, a microphone Ml being connected to the input of apparatus TA and a loud speaker LS being connected to the output of apparatus RA. The communication apparatus would be preferably the same for each train and the transmitting apparatus TA and the receiving apparatus RA are shown conventionally for the ,sake of simplicity since their specific construction forms no part of my present invention and it may be any one of several well-known constructions. For example, such communication apparatus may be of the construction covered by Letters Patent of the United States No, 2,064,639, granted December 15, 1936, to L. D. Whitelocl: et al., for Communicating system. An oflice indicated at OP is provided with communication I apparatus comprisin transmittin app ra us TA and receiving apparatus RA, which would preferably be of a construction the same as that on trains VI and V2.

Two line wires LI and L2 extend along the railway. These line wires may be, for example, open wires placed on a pole line along the; right of way. Wires LI and L2 are preferably transposed in the usual manner at preselected loca i paratus active at a time. It is apparent, of course,

that the transmitting and receiving apparatus of repeater station WA may be omitted if desired,

. using only the repeater equipment.

It is clear that current from the oflice transmitting apparatus TA is applied to the line wires LI and L2 in multiple, the line wires in-multiple'serving as one side of a line circuit and the-ground path serving as the other side of such circuit. However, current is received by the office receiving apparatus RA from the line wires LI and-L2 in series. i r

The dash and dot rectangle WA indicates a wayside station at which repeater equipment is provided. This repeater equipment comprises an amplifying tube VTI and two transformers TI and T2. Tube VTI is provided with a gridcircuit including a winding 5 of transformer T2 and a biasing battery 6, and with a plate circuit including winding 1 oftransformer TI and a source of current, such as a battery 8. A winding 9 of transformer TI is connected across line wires LI and L2, while a mid terminal of winding "9- is connected to a ground electrode I0 through a winding I I of transformer T2. A portion of current flowing in the two line wires LI and L2 in multiple, as indicated by solid line arrows, flows to ground through the two portions of winding 9 of transformer TI to its mid terminal and thence through winding II of transformer T2 to ground electrode I0. Such current induces in winding 5 of transformer T2, a corresponding electromotive force which is applied tothe grid of tube VTI to be amplified in the plate circuit of the tube causing thereby a corresponding electromotive force to appear across the outside terminals of winding 9 of transformer TI with the result that such repeated current fiows in the linewires LI and L2 in series as indicated by the dotted line arrows. In other words, current supplied toline wires LI and L2 in multiple, as for exam ple by the transmitting apparatus of oflice OF, is amplified and reapplied to the line wires LI and L2 by the repeater equipment, the reapplied current flowing in the line Wires in series.

As shown in Fig. 1, the repeater station WA is also provided with transmitting apparatus TA and receiving apparatus BA for communication from that station. Apparatus TA and apparatus RA of station WA would preferably be similar in construction to that provided for trains- VI and V2. The output terminals of apparatus TA of station WA are connected to a' winding I3 "of transformer T2, and the input terminals of apparatus RA are connected to a winding I2 of transformer TI. Current supplied by the trans{ mittlng apparatus TA of station WA induces in winding 5 of transformer T2 a corresponding electromotive force which is amplified by'tubeVTI and applied by transformer TI to line wires LI and' L2 in series. Communication current sup Circuit connections between line wires LI and L2 and the rails of the different tracks are provided at various preselected points along the railway, two such connections being shown at points PI and P2, one on each side of the repeater station WA. These circuit connections are preferably all alike, and a description ofthat at point PI will suffice for an understanding of all. A transformer T3 has a primary winding I4 connected across line Wires LI and L2, while a mid terminalof winding I4 is connected to a ground electrode I5, over a path including two asymmetric units I6 and IT in mu1tiple,and disposed reverse to each other, and windings I8 and I9 in multiple of two transformers T4 and T5, re spectively. Two, resistors 2| and 22 are connected across the rails of tracks I and 2, respectively, and a winding 20 of transformer T4 is connected between the mid terminals of resistors 2I and 22, while a midterminal of winding 20 is connected to ground electrode I5through a winding 23 of transformer T3. Similarly, two resistors 24 and 25 are connected across the rails of tracks 3 and 4, respectively, and a winding 26 of transformer T5 is connected between the mid terminals of resistors 24 and 25, while a mid terminal of winding 26 is connected to ground electrode I5 through a winding 21 of transformer T3. I

In describing the operation of the apparatus of Fig. 1, I shall first assume that communication is desired between the two trains VI and V2, and that at the starticurrent is transmitted from train VI to train.V2. Furthermore, I shall assume that train VI is relatively near the point PI and train V2 is relatively near the point P2.

'Current from transmitting apparatus TA on train VI is applied to the track rails of track I through the wheels and axles 28 and 29 of train VI, and current flows in the rails in multiple to each side of train VI and through the rail-to-ground path in the well-known manner. Some of the current flowing in the rails to the west of train VI flows through resistor 2 I, winding 20 of transformer T4, and resistor 22 to the rails of track 2, and thence through the rail-to-ground path oftracks 2 and I back to the point at which the current was first applied tothe rails of track I. Current flowing in winding 20 of transformer T4 creates a corresponding electromotive force across winding I8 of that transformer and current is transferred to the line wires through the circuit connection at point PI. Such current flows at a given instant say, from the lower terminal of winding I 8 over asymmetric units I5 and I! in multiple, the two portions of winding I 4 of transformer T3 to its mid terminal, line wires LI and L2.:inmultiple; thetwo portions of winding 9 of transformer TI at station .WA, Winding II of transformer T2, ground electrodes I0 and I5 and to the top terminal of Winding I8 of transformer T4, That portion of the current flowing through winding H'of transformer T2 of the repeater equipment is amplified andreapplied to the line wires LI and L2 in series in the mannerexplained hereinbefore, with substantially one-half of such current flowing to the west and one-' half to the east of station WA. At point P2, a part of the current flowing in line wires LI and L2 in series flows in winding 33 of transformer- T6 to transfer energy to winding 3| of that trans former and cause current to flow from winding 3| over a path including ground electrode 32, a rail-to-ground path for each of the tracks 3 and 4, resistors 33 and 34 connected acrossthe rails of tracks 3 and 4, respectively, winding 35 of transformer T1 to a mid terminal and thence back to winding 3! of transformer T3. That portion of the current flowing in the rails of track.- T4 is available to excite a receiving coil 36mounted on train V2 in inductive relation to the rails and connected to the receiving 'apparatus'RA of train V2. Transmission of current from train V2 to train VI is effected in a manner similar to that just described: for transmission from train VI to train V2, and the description need not be repeated. It is apparent from the foregoing description that communication current would be transmitted between two trainsspaced apart on any one of the tracks, or between trains on any two of the tracks of Fig. 1 in substantially the same manner as described for transmission of current between trains Vi and V2.

In communication from office OF to a train, such as train V2, current applied at the office to the line wires Li and L2 in multiple is. repeated and amplified at station WA to flow in the line wires LI and L2 in series, and a portion of such reapplied current is transferred. to. the rails of track 4 through the circuit connection at. point P2 in the manner explained hereinbefore. to. excite the receiving apparatus of train V2. Cur-. rent supplied to the rails of track 4 by train V2 is transferred to line wires LI and L21 in multiple in a manner similar to that explained in connection with the current supplied to the rails at train VI, and the current supplied to: line wires LI and L2 in multiple from track T4 is repeated and amplified at station WA to cause current to flow in line wires LI and L2 in series, which reapplied current is available to excite the receiving apparatus at office OF through winding 5! 1 of transformer Tl2.

Communication between station WA and either train Vi or V2 is efiected over line wires Li and L2 and the connections at points PI and P2. Cur

rent from the transmitting apparatus TA of sta tion WA is applied through winding 13 of transformer T2 to the amplifier tube VTI and thence to the line wires in the manner explained hereinbefore. Such current flows in the line'wiresLi and L2 in series and is transferred atv points, P! and P2 to the rails of the differenttracks for exciting receiving apparatus of .a train moving on any one of the tracks. Also currentlsupplied to a track, for example, by train V2 to track 4, is transferred through the connection at point P2 to the line wires LI and L2 in multiple, and is applied to the equipment at station WA to induce in winding l2 of transformer Ti a corre sponding electromotive force which is available to excite the receiving apparatus RA of station WA. I

The asymmetric units, such as units l6 and 11, included in each circuit connection between the line wires and the track rails are preferably of the dry surface type such ascopper oxide rectifier elements which are. characterized by arelatively low impedance. for a current: of large value and a high impedance for current. of low value. These units are insertedin the. circuit connection to offer a relatively low impedance to current of relatively large value and a relatively high impedance to current of a relatively low value. Current is thus transferred to the line wires at a connection in the. vicinity of a train with little attenuation because the communication current flowing in the rails is of relatively large value and the units offer low-impedance. At some distance away from the train the line current becomes weaker. and the asymmetric units offer a higher impedance, and thereby prevent the energy from being wasted .by feeding back into the track rails at these distant points. Such asym metric units only serve as an aid and may not be required.

Since the attenuation of the communication current is small in the. line wires LI and L2 in multiple, and since the power required to energize each repeater station amplifier is small, the original energy applied to the line wires LI and L2 may be amplified and distributed at several different repeater stations, and thus transmission effected over a relatively long distance along the railway. Also, since the direction of the flow of current in the rails is reversed at adjacent circuit connections due to the transposition of the line wires, there islittle danger of the rail current feeding back into the line wires and setting up excessive regeneration.

Referring to Fig. 2,, a line wire L3 extends along a railway of which only track I is shown, and on which track I a. train V3 provided with communication apparatus is moving. Line wire L3 is included in a line circuit formed by line wire L3 as one side and the ground path as the other side. Ofiice OF of Fig. 2 is provided with communication apparatus connected to line circuit through a transformer TI 5, whose winding 10 is connected between line wire L3 and a ground electrode ll while the output terminals of transmitting apparatus TA are connected to a winding 12 of transformer'Tl5, and the input terminals of receiving apparatus RA are connected to a winding 13 of transformer Ti 5. A wayside station WA is provided with repeater equipment comprising an amplifier tube VTI and transformers T3 and T9. Tube VTI of Fig. 2 is provided with a grid circuit including winding 31 of transformer T8 and a biasing battery 38, and with a plate circuit including a winding 39 of transformer T9 and a suitable source of current. Winding 43 of transformer T8, a condenser 84 and a resistor. are interposed in a connection between line wire L3 and a ground electrode 42, while winding 43 of transformer T9 is included in a circuit between a mid terminal of winding 4!] and the terminal of resistor 4| adjacent ground electrode 42. A portion of communication current flowing along line wire L3 flows to ground at station WA through the line-to-ground connection, and an electromotive force is induced in winding 31 of transformer T8 to be applied to tube VTI to cause an amplified current to appear in the plate circuit, and which plate current is fed to the mid terminal of winding 43 of transformer T8 to create a voltage across the lower portion of winding 49 and resistor 4|. This voltage caused by the amplified current causes current to flow in the line circuit and which current reinforces the original communication current flowing in the line circuit. At points toward the source of the original current, the amplified current might tend to cancel the original current. However, the amplified current must be exactly 180 degrees out of phase for cancellation of the original current, and such phase relation will'rarely, if ever, occur because of the inductance of the various circuits. The largest advantage for points beyond the repeater station occurs when the amplified current and the original current are in phase, but this condition will be rare; However, the amplified current is much stronger than the original current, and the resultant would be a current much larger than the original. Such repeater equipment can be spaced apart as required along the railway for propagation of the communication current over relatively long distances.

Circuit connections are provided between line wire L3 and the rails of track I at various points, and of which circuit connections those at two points P3 and P4 only are shown in Fig. 2 since these are suflicient to fully illustrate the invention. These circuit connections are preferably all alike, and looking at the circuit connection at point P3, a transformer TID has one winding 44 connected between line wire L3 and aground electrode 45 while its other winding 46 is connected between a ground electrode 48 and a mid terminal of a resistor 41 connected across the rails of track I.

Assuming current is supplied to the rails from the transmitting apparatus TA of train V3 to flow in the rails and the rail-to-ground path, a portion of such current flows between the rails and ground through resistor 41 and winding 46 of transformer TIIl at point P3, and a portion fiows between the rails and ground through winding 49 of transformer TI I at point P4. The connections of transformers TIII and TH are such that the relative polarities of the energy transferred to winding 44 of transformer TIII and to winding 50 of transformerTI I cause currents to flow in line wire L3 which pass through the line to-ground connection at the repeater station WA in the same direction. The resultant current, after amplification by the repeater equipment, is fed back to line wire L3 to reinforce the original current in the manner explained hereinbefore. At ofiice OF a portion of such current flows from line wire L3 to ground through winding II! of,

transformer TI5 to excite the receiving apparatus RA through winding 13 of transformer TI5. Transmission of current from the transmitting apparatus of ofiice OF to the receiving apparatus of train V3 is accomplished in a similar manner and the description need not be repeated.

In Fig. 3 there is shown apparatus to facilitate the transmission of communication current between an oflice and a train at any point of a railway division, which division may be of 100 miles or more in length. Line wires LI and L2 are shown as extending from oflice OF along the division of the railway, of which the two tracks I and 2 are shown. The oflice OF of Fig. 3 is provided with communication apparatus similar to that at the office OF of Fig. 1.

At some point distant from ofiice OF, such as for example, the central point of the railway division, a repeater station WB is located. The repeater equipment of station WB comprises an amplifying tube VT2 and transformers TI3 and TI4, together with a winding 58. Winding 58 is connected across line wires LI and L2, while its mid terminal is connected to ground electrode 59 through a winding 60 of. transformer TI3 and a resistor GI. Hence a portion of. communication current supplied to line wires LI and L2 in multiple at the ofilce OF flows to ground through winding 60 of transformer TI3 to transfer energy to winding 62 of transformer TI'3, and which energy is applied to the grid of tube VT2 to be amplified in the plate circuit of that tube, the plate circuit including a winding 82 of transformer TI4. Such plate circuit current flowing in winding 82 causes energy to be transferred to winding 63 of transformer TI 4 and applied to the mid terminal of winding 60 of transformer TI3 so that a portion of the amplified current is reapplied to the line wires LI and L2 in multiple to reinforce the original current flowing in the line wires. That is, the current supplied at the ofiice OF to line circuit including wires LI and. L2 in multiple, is amplified by the equipment of station WB and reapplied to the same line circuit to flow in the line wires LI and L2 in multiple. If required, other repeater stations similar to that of station WB may be provided along the railway division, but since the attenuation of the current in the line wires would be relatively small, one such repeater station for a division may be all that would be required.

Repeater equipment is also provided at each of a plurality of other locations to repeat and amplify the current flowing in the circuit including line wires LI and L2 in multiple and cause current to flow in the circuit including line wires in series for transfer to the rails of the various tracks. Two such repeater stations WAI ,and WA2 are shown in Fig. 2, one station on each side of the repeater station WB. Each repeater station WAI and WA2 is provided with repeater equipment of the same construction as that of station WA of Fig. 1, except that an indirect heater type of amplifying tube is used, and a condenser-resistor biasing unit replaces the biasing battery 6 of the equipment of Fig. 1.

Circuit connections between the line wires LI and L2 and the rails of tracks I and 2 of Fig. 3 are provided at various points along the division, and of which points only four points P5, P6, P1 and P8 are shown. These circuit connections'of Fig. 3 are substantially the same as shown in Fig. 1 for tracks I and 2 except the asymmetric units are omitted and the rails of track 2 are used as a ground electrode. In Fig. 3, a train V4 provided with communication apparatus is shown as occupying track I in the vicinity of the repeater station WA2.

In communication between ofiice OF and train V4, current is supplied to line wires LI and L2 in multiple at the office and this current flowing in the line wires in multiple, is repeated at station WB and then that portion of the repeated current supplied to the line wires is again repeated by the equipment of station WA2 to cause current to flow in the line wires in series. This latter current is transferred to the rails of track. I through the circuit connections at points P1 and P8 and is available to excite the receiving apparatus of the train V4. Current applied to the rails of track I by train V4 is transferred to the line wires LI and L2 through the circuit connections at points P1 and P8 t flow in the line wires in multiple, and such current is repeated at station WB to reinforce the original current flowing in the line wires in multiple. At a repeater station near the office, such as station WAI, the current is amplified and reapplied to the line wires to flow in the line wires in series, and such current flowing in the winding of transformer TI 2 at the oflice induces a current in winding 51 which is available toexcite the receiving apparatus RA of-theoflice;

Although I have herein shown anddescribed but three forms of apparatus for railway train communication systems embodying myinvention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scopeof my invention.

Having thus described my invention, what I claim is:

1. In apparatus for a railway train communication system, the combination comprising, circuit means including a line wire extending along a railway for transmitting communication current to difierent points along the railway a first station provided with transmitting apparatus coupled to said circuit means to cause communication current to flowin the line wire, repeater equipment including an electron tube'amplifier at a preselected location along the railway and connected to said circuit means xto repeat in the circuit means such communication current in amplified form, and train carried receiving apparatus mounted on a train ,movingon a track of said railway and coupled to said circuit means to be efiectively energized by the communication current flowing in said circuit means due to the amplification effected by said repeater equipment.

2. In apparatus for a railway train communication system, the combination comprising,aline wire extending along a railway, a station provided with transmitting apparatus coupled -to said line wire to cause communicationcurrent to flow in the line wire, repeaterequipment in cluding an electron tube amplifierplacedat a preselected location along the railway-and having connection to said line wire toreceive said communication current and cause such :current in amplified form to flow in the line wire, a cir.- cuit connection to connect saidline wire tothe rails of a track of said railway at a location preselected with respect to the location of said repeater equipment, and train-carried receiving apparatus including a circuit coupled to the rails and effectively energized by the communication current transferred tothe rails through said circuit connection dueto the amplification effected by said repeater equipment --when the train occupies said track in the vicinity of said circuit connection.

3. In apparatusfor a-communicationsystem, the combination comprising,-a first circuit including two conductors in multiple as one side of the circuit and another conductingpath as the other side of the circuit, transmittingvapparatus connected across the two sidesof said first circuit'to cause communication-current to flow therein, repeater equipment including an electron tube amplifier havinginputterminalsconnected across the two sides-'of-first circuit and output terminals connected across said two conductors to repeat in amplified form the communication current flowing in saidfirstcircuitdn another circuit including said two conductorsin series, and receiving apparatus coupled to said other circuit effectively energized by thecommunication current thus caused'to flow'in said other circuit.

4. In'apparatus for a communication system, the combination comprising, a first circuit including two conductors inmultiple as-one side of the-circuit andaanother conducting path as the otherside of the circuit, transmittingrapparatus connected across the ,two sides of said first circuit to cause communication current to flow therein, an electron amplifier tube having a plate, ,a cathode and agrid; a first winding connected across said two conductors, a second Winding coupled to said first winding and included in a plate circuit connected to the plate and cathode of saidtube,at-hird'winding interposedhetween a mid terminal of said first winding and said other conducting path of said first circuit, a fourth winding coupled to said third winding and connected across'the grid 'and'cathode of said tube to cause the amplifying of the communication current flowing in said first circult and the supplying of such amplified current to a second circuitincludingsaid two conductors in series, and receiving apparatus coupled across said two conductors eiiectively energized lay the communication current thus caused to flow in said second circuit.

5. ,In apparatus for a railway-traincommunication system, the combination com-prisingtwo line wires extending along a railway, a station provided with transmitting apparatusha-ving-one terminal connectedto said'two line wires in multiple and another terminal connected to ground tocause communication current to flow in the two line wires in multiple, repeater equipment ata preselectedxlocation along said railway-and having its input side connected between the two line wires in multiple and ground and its output side connected across said two line wires to receive said communication current from the two line wires in multiple and reapply such current to the two line wires'in series, a circuit connection at a point preselected with respect to said repeater equipment location connected across the two line wires and to the two rails of a track of said railway to transfersuch current flowing in the line wires in series to the rails of said track, and train carried receiving apparatus including a circuit coupled to therails effectively energized by such current thus transferred'tothe rails when the train occupies said track in the vicinity of said circuit connection 6. In a railway train communication system, the combination comprising,-alinewire extending along a railway, a station provided with transmitting means connected between said line wire and ground to cause communication current to flow-in said line wire,repeater means including an electron tube-and a-first and a-second transformer located at a preselected location along therailway, saidfirst transformer'having a first winding connected bet-ween said line wire and ground and a second'windinginterposed in a grid circuit of said tube and saidsecond transformer having a first winding interposedin a plate circuit of said tube and a second winding connected between a mid terminalof said first winding of the first transformer andgroundto reinforce the original communication current flowing in said line wire-by such current amplified 'bysaid tube, a circuit connection;includ-ing transformer meansconnected{between said line wire and the rails of .aftra-Qk of said railway to transfer such current :from said line wire; to the rails of said track and train ;carr ied receiving means including :a vcircuit coupled {to the rails and effectively energized by-the current thus transferred to-the .rails when thetrain'occupies said track.

7. In a railway traincommunicationsystem, the combination comprising, apaii' of linewires extending along a multiple track railway, re-

peater equipment including an electron tube and a first and a second transformer at a preselected location along said railway, said first transformer having a first winding connected across said line wires and a second winding interposed in a plate circuit of said tube and said second transformer having a first winding connected between a mid terminal of the first winding of the first transformer and ground and a second winding interposed in a grid circuit of said tube to repeat communication current flowing in a circuit including the line wires in'multiple in another circuit including the line wire in series, two circuit connections one at each of two points on opposite sides of said repeater location, each said circuit connection including transformer means having connections to the rails of each track of said railway and to said line wires for transferring communication current from the rails of any track to the circuit including the line wires in multiple and from the circuit including the line wires in series to the rails of each of said tracks, a first train moving on one track of the railway and provided with transmitting apparatus effective to supply such communication current to the rails, and a second train moving on another track of the railway and provided with receiving apparatus coupled to the rails and effectively energized by the current supplied by said first train transmitting apparatus due to said circuit connections and said repeater equipment.

8. In a railway train communication system, the combination comprising, a pair of line wires extending along a multiple track railway, repeater means including an electron tube amplifier at a preselected location along the railway, means to couple the input side of said amplifier to a connection between said line wires in multiple and ground and to couple the output side of said amplifier across said line wires, two cir-; cuit connections one at each of two points on opposite sides of said repeater location; each said circuit connection including transformer means having connection to said line wires, to ground and to the rails of each track of said railway for transfer of communication current between the line wires and the rails of each track of the railway; and two train carried stations spaced apart along said railway and each station provided with transmitting apparatus effective to supply communication current to the rails and receiving apparatus energized by such current flowing in the rails for communication between said two stations due' to said circuit connections, said line wires and said repeater means.

9. In a railway train communication system, the combination comprising, two train carried stations spaced apart along a railway and each provided with transmitting apparatus coupled to the rails of a track of the railway to supply communication current thereto and receiving apparatus coupled to the rails to receive such current therefrom, a line wire extending along sail railway, a circuit connection at each of a plurality of preselected points along the railway and each including transformer means having connection to the rails of each track of the railway and to said line wire for transfer of such communication current from the rails to the line wire or from the line wire to the rails, and repeater means including an electron tube amplifier connected to said line wire to repeat 'in amplified form such communication current flowing in said line wire to aid communication between said two stations.

10. In a railway train communication system, the combination comprising, two train carried stations spaced along a first and a second track of a multiple track railway and each provided with communication apparatus coupled to the rails to supply communication current thereto and to receive such current therefrom, a pairof line wires extending along the railway, a circuit connection at each of a plurality of preselected points along the railway and each of which connections includes a first and a second trans former, a first winding of said first transformer connected across said line wires while a first winding of said second transformer is connected between the rails in multiple of the first track and the rails in multiple of the second track and the second winding of the first transformer is connected between ground and a mid terminal of the first winding of the second transformer and the second winding of the second transformer is connected between ground and a mid terminal of the first winding of the first trans former whereby current is transferred from the line wires in series to the rails in multiple of each track and from the rails in multiple of either track to the line wires in multiple, and repeater means including an electron tube amplifier connected to said line wires to receive current from the line wires in multiple and to reapply the current in amplified form to the line wires in series to aid in communication between said two stations.

11. In a railway train communication system, the combination comprising, a pair of line wires extending along a railway, an oifice provided with communication apparatus effective to supply communication current to a first circuit including said line wires in multiple and ground and to receive such current from a second circuit including said line wires in series, a first repeater station including an electron tube amplifier connected between said line wires and ground to repeat 'in amplified form the current flowing in said first circuit, a second repeater station including an electron tube amplifier having its input connected between the line wires in multiple and ground and its output connected across said line wires to repeat in amplified form the current flowing in said first circuit in saidsecond circuit, a circuit connection including transformer means connected between said line wires and-to the rails of a track of said railway for transfer of such communication current, and a train carried station provided with communication apparatus coupled to the rails to supply such current thereto and to receive such current therefrom for communication with said ofiice through the medium of saidcir cuit connection and said first and second circuits. I

12. In a railway train communication system. the combination comprising, a pair of line wires extending along a railway, an ofiice provided with communication apparatus effective to supply communication current to a'first circuit including said line wires in multiple and ground and to receive such current from'a second circuit including said line wires in series, a first repeater station at a preselected location along the railway and including an electron tube amplifier having both its input and output sides coupled to said first circuit to reinforce the communication current flowing in said first'circuit at said preselected location, a second repeater station located at another preselected location along the railway and including an electron tube amplifier having its input side coupled to said first circuit and its output side coupled to said second circuit to repeat in said second circuit the current flowing in said first circuit, a plurality of circuit connections one at each of a plurality of preselected points along the railway and each such circuit connection including transformer means coupled to the rails of a track of the railway and to each of said first and second circuits to transfer current between said rails and said circuits; and a train moving on said track provided with communication apparatus capable of supplying such communication current to the rails and to receive such current from the rails for two-way communication with said ofiice by the medium of said circuit connections, said repeater stations and said first and second circuits.

13. In a railway train communication system, the combination comprising, a pair of line wires extending along a railway, a line circuit including said pair of line wires in multiple as one side of the circuit and the ground path as the other side of the circuit, transmitting apparatus at a first location along the railway and coupled to said line circuit to supply a communication current thereto, a repeater station at a preselected location along the railway and including an electron amplifier tube and a first and a second transformer, said first transformer having a first winding interposed between said line wires in multiple and ground and a second winding interposed in a grid circuit of said tube and said second transformer having a first winding interposed in a plate circuit of said tube and a second winding interposed between a mid terminal of the first winding of the first transformer and ground to repeat in amplified form in said line circuit at said preselected location the communication current supplied to the line circuit at said first location, and receiving apparatus coupled to the line circuit effectively energized by the communication current due to the amplifying of the current at said repeater station.

WILLARD P. PLACE. 

